Image: Photograph by Amy Eckert
In Brief
- Migration of plants, animals and other species outside their native ecological niches represents a danger overhyped by some ecologists, contends a scientist who once decried such threats.
- Mark Davis of Macalester College asserts that we should worry about invasive species only when they create a direct threat to health or economic well-being. Extinctions from invaders remain the exception. Nonnative species do not usually drive out plants and animals when they reach a new place.
- Isolated places, such as islands, represent the one setting in which the nonnatives can frequently cause the endemic population to disappear.
- Davis maintains that we simply must get used to the reality that species do not stay put.
Plant ecologist Mark A. Davis will not participate in this year’s “Buckthorn Roundups” around his St. Paul, Minn., neighborhood. Davis will not tag along as these intrepid crusaders set out to eradicate the common and glossy buckthorn, two ornamental shrubs imported in the 19th century from Europe. The nonnatives have now taken over some Midwestern forests, prairies and wetlands. That is why eco-minded volunteers eagerly wrench young weeds from the soil, hack away at thick stems and douse remaining stumps with herbicides. Their hope: a return of Minnesota to its primeval state.
At one time, Davis, too, could see the logic in eradicating these “invaders.” He even advocated planting only Minnesota native plants on the Macalester College campus where he teaches. That changed in 1994, when he read an essay by journalist Michael Pollan in the New York Times Magazine that made his blood boil. He bristled at Pollan’s statement that turning the “ecological clock to 1492 is a fool’s errand, futile and pointless to boot.”
This article was originally published with the title A Friend to Aliens.
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12 Comments
Add CommentDavis maintains that we simply must get used to the reality that species do not stay put.... That is a very true statement, but humans do not need to help species 'not stay put'. When we intentionally bring invading species into an area, we set the stage for an ecological disaster. Look at what we did in Arizona when we started planting rapid growing trees so the senior people, who moved there so they could breathe fresher, cleaner air, could have shade and not get so hot and have a heat stroke...we created an allergy nightmare. When nature brings in the species, native species have time to adapt. When humans brings in the species, we must regulate them until native species have time to adapt, and if the native species do not have time to adapt before the invading species take over, then we must remove the invading species from that area. That is common sense professor, the kind you had before you read that article.
Reply | Report Abuse | Link to thisAs things warm up and environments change Alien species will be necessary to maintain an ecology. Certain plants though are not of help to certain etiologies though. The salt cedar for example, robs the available water in a destructive way. Not something that one leaves growing in a dessert.
Reply | Report Abuse | Link to thisA study needs to be done to assess which alien species are helpful locally and which are destructive. As of now its assumed all alien species are destructive. Logic says that some must be helpful. But nature purest dont look beyond what 'shouldn't' be there.
Birds have been the main vehicle of plant migration so alien species isnt unnatural by any means. Ancient man also played a huge roll in what species are present in many locations. It would be naive to assume that todays migration of species isnt in some way normal. But still studies need to be applied before one can just assume whats best.
In Australia we suffer the consequences of wholesale imports of animal and plant species. Flies, rabbits, foxes, minas, cane toads the list goes on. We got to learn to live with them now, many native species were lost as a result, however the principal loss of species is driven by man's destruction of habitat.
Reply | Report Abuse | Link to thisEuropean farming practices also created mayhem here, destroying the land like never before. One man who realised this and reverted to pre European landscape has succeeded. We had a massive amount of rain this spring and early summer, not unusual: Dorothea McKellar wrote in the 19th century.
I love a sunburnt country,
A land of sweeping plains,
Of ragged mountain ranges,
Of droughts and flooding rains.
I love her far horizons,
I love her jewel-sea,
Her beauty and her terror –
The wide brown land for me!
This is verse 2 of her poem My Country.
The person who came up with what he calls Natural sequence Farming is Peter Andrews. His methods were proved by the floods. Millions of tons of topsoil were lost in the brown waters, the farms designed on his principles gained topsoil. Dr. Alison Bleaney a GP from Tasmania also proved Peter right when she discovered weird rare diseases were common in her rural practice, in the most beautiful natural surroundings. The culprit was the beautiful mono cultural timber plantations whose shed leaves poisoned the surface waters of local streams.
We have to live with our past actions, but lets act with constrain in the future. want to know more.
http://www.naturalsequencefarming.com/ for Andrew.
http://www.abc.net.au/austory/specials/somethingwater/default.htm for Alison's story.
It's about time someone fessed to the reality that the earth is changing. People will often say that they "believe in evolution" when they really don't. Evolution is change. Similarly, while I don't think that the wholesale exploitation of the earth and its resources is a good idea, some global warming is probably inevitable.
Reply | Report Abuse | Link to thisWhen I lived in Hawaii, I would go to my favorite coffee shop and listen in on the various discussions. One of the favorite topics was INVASIVE SPECIES. People would carry on about the evil invasive species and what could be done. I suggested that they leave Hawaii because humans and their domesticated companions, dogs, cats, pigs, etc. were the most virulent species that had been introduced. They would chuckle and go back to their ranting. I would also suggest, somewhat tongue in cheek, that they hold a yearly contest to select the best new species to introduce. This would get a more lively response. Heck, there are already fleas, mosquitoes and coqui(sp?) frogs, why not something more interesting. No one thought it was funny. The world is changing. Get used to it.
Ratus ratus, almost a bad of an exotic plague as Homo not so sapian
Reply | Report Abuse | Link to thisHere in California, the native plant movement has a death grip on our public lands. They have destroyed hundreds of thousands of non-native trees and they will destroy millions more if permitted and funded by taxpayers. Since much of California was virtually treeless, their success dooms us to a treeless landscape of grassland, chaparral, and scrub.
Reply | Report Abuse | Link to thisThe destruction of our non-native forests damages the environment in many ways. The most obvious way is that untold gallons of toxic herbicides (usually Garlon with active ingredient triclopyr) are used to kill non-native vegetation and the roots of the trees that are removed, which would otherwise resprout without repeated dousing of herbicides. The herbicides are most harmful to aquatic life, and moderately toxic to birds and bees. Other animals are probably harmed but since the EPA's testing protocols are very limited, we know little about these chemicals before they are made commercially available.
Equally insidious is that hundreds of thousands of tons of carbon are released into the air when trees are destroyed and decay after being chipped and scattered to help prevent erosion (often unsuccessfully). Carbon dioxide is the predominant greenhouse gas which contributes to climate change. The great irony is that the native plants that theoretically benefit from all this destruction are no longer sustainable in their historic ranges because the climate has changed and will continue to change. The tree destruction accelerates this process.
Please visit the Million Trees blog (http://milliontrees.wordpress.com) to learn more about the harmful impact the native plant ideology is having on our environment. It is not only futile. It is also harmful.
Thanks to Professor Davis for helping to educate the public about the destructive aspects of the native plant ideology and to Scientific American for giving Professor Davis this venue.
Mr. Davis cannot be more off tune. I think the distinction that needs to be is the difference between alien species and invasive species. The term "invasive" means something and that is that the species has negative impacts. Take European buckthorn for example: This species not only changes the plant life around it by shading out most plant species it also has the ability to change the soil chemistry and nutirent levels that provides excellent habitat for it to grow more robust and spread. Its berries are not that well liked by bird species therefore it has an abundance of seeds that survive to further propagte the species. it also is determental by decreasing herbaceous species that hold the soil together. Buckthorn causes lots of soil erosion.
Reply | Report Abuse | Link to thisNow an alien species might not even be noticed in the landscape and present no ecological concerns at all like daylilly, corn, potatoes, lilacs etc. yet it is still introduced but could be left alone in native settings and have little or no impact.
Invasive species by nature do have an ecological impact and most of them need to be addressed not only with eradication but also long-term management.
we can not be naive to believe that invasives have no impact and that letting nature take its course is a sustainable action by humans. Biodiversity is the key to life and we as humans are smart enough to recognize this and do something about.
Mr. Davis you will be miss on those wonderful days where the restoration community gathers to lend a helping hand, even the native Americans did this.
Davis says, "we should worry about invasive species only when they create a direct threat to health or economic well-being." The irony of that statement is that by allowing aggressive/invasive species to establish themselves and create a mono-culture that eradicates all else, the threat is already in place, and extinction of native species occurs. The point of controlling invasives is to prevent this direct threat. If we wait for the threat to occur first, we waste time, effort, money and all the scientific proof from other ecologists and on the ground efforts that contradicts Davis's claims. Biodiversity is the key to healthy air, water and life both human and non-human.
Reply | Report Abuse | Link to thisThe article comments that Davis will “not tag along as these intrepid crusaders set out to eradicate the common and glossy buckthorn, two ornamental shrubs imported in the 19th century from Europe.” Davis contradicts himself with the following statements “The one environment where introduced species can and absolutely have caused lots of extinctions are in these insular environments such as oceanic islands or freshwater lakes.” and he continues to say “In those sorts of habitats, absolutely, introduced species are a major threat to species survival, and I certainly support dedicating resources to prevent that.”
Reply | Report Abuse | Link to thisThe contradiction comes in to play because the destruction of most of our natural areas in the Midwest has turned the remaining isolated natural areas into “insular environments” in the terms of Mr. Davis. This is Island Biogeography 101 and Davis should know this as an ecologist. Whether predator or not invasive species such as buckthorn had and continue to have the same ill effect of species extirpation in these insular modern natural areas.
If large unbroken tracts of natural areas remained with many of the natural processes working as they did prior to our initial and continued disturbance, invasive species would not be such a problem. Island biogeography and edge effect causes the disturbance and lack of natural process in our Midwest natural areas, which requires us to artificially simulate these natural processes through management to preserve the biodiversity. If biodiversity continues to crash as it has been it will certainly be a health and economic threat to us humans.
Yes we can live to learn with the non-native species, but we must reduce the invasive species to a tolerable ecological threshold. I think Mr. Davis should reevaluate his statements regarding invasive species management.
This is Fox News style reporting. I expect better from Scientific American. One dissenting voice against general scientific consensus.
Reply | Report Abuse | Link to thisTry reading Alfred Crosby's Ecological Imperialism to put things in perspective. A lot of species are here to stay and they have done what they were going to do. Some did great damage along the way. It doesn't mean new species get a free pass. It doesn't mean we stop using science to predict new threats, or to cope with such threats as they emerge.
Mr. Davis would have us not worry about species unless they are a "direct threat to health or economic well-being". Mr Davis is God that he knows a bad species from a good one, the whole lambs from goats thing? Tell the Hawaiians who thought sex with whalers was a good idea and died of venereal disease for their friendliness? Or planted fountain grass on the Big Island to feed their cattle only to find it explodes into flame, burning native forest and threatening to torch firefighters and houses.
Such omniscience! His talents really should be focused on the stock market!
I am sure he would be most welcome to share his views on rabbits and cats in any Australian bar. As long as he keeps shouting the next round of beer, he should emerge unscathed. ;)
Mr Davis chooses to overlook a very important fact. It is true that species have been on the move from the beginning of life and that this is perfectly natural. What is not natural is the accelerated rate of species introductions into other ecosystems by the hands of humans and this is where the problem is.
Reply | Report Abuse | Link to thisEcosystems are like symphonies. It takes millions of years of co-evolution to develop a fine tuned system, richly complex and delicately balanced. If you took a well crafted symphony and added a snippet of music from another composition, the introduced segment wouldn't fit with the rest of the work. The composer could weave this addition into the symphony by tweaking the alien fragment and the related parts until it all worked well together once again. It would take some time and effort but it can be done. However if a large number of musical fragments are introduced it becomes impossible to repair the piece. Likewise ecosystems have been dealing with introduced species all along; it may take many thousands of years, perhaps millions, but eventually the non-native species become part of the ecosystem. Unfortunately, in recent times, humans have been moving species around, intentionally and unintentionally, at unprecedented rates. The numbers of species invading new environments far exceed the pace of evolution; ecosystems suffer serious disruptions as a consequence.
One of the big problems is that people such as Bothrops claim that there is "general scientific consensus" but for what? For pouring herbicides on natural areas? I don't think so. These kind of complex compound molecules don't even exist in nature without man's refining them. How can they be natural?
Reply | Report Abuse | Link to thisBureaucrats who rely on public land management for their income have a built in bias - a conflict of interest in always prescribing that something needs to be done when they are the ones that are also going to be paid to do it. That's why, especially in the midwest and eastern U.S., there is little or no land that has been left to succeed naturally, and we are losing the expertise of nature in figuring out how to deal with the growing list of ecological problems.
The science of ecological succession tells us that such areas are important. Natural areas are being overmanaged and exotic species is a worn out reason to keep doing it.